Drainage system

ABSTRACT

A drainage system having a stack, a branch piping and a relief vent for reducing positive pressure in the drainage system. The relief vent is connected to the branch piping between the stack and the trap of the fixture. The relief vent is a unidirectional vent which opens automatically upon the application of positive pressure at the first end of the passageway of the flexible vent member and closes automatically when the pressure is reduced. The drainage system may also include an air admittance valve to relieve negative pressure in the drainage system.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a drainage system having vents to allowfor equalization of the pressure in the system. In particular, thedrainage system of the present invention has relief vents to allow gasesto escape the system to reduce positive pressure in the drainage system.In one (1) embodiment, the drainage system may also have air valves toallow gases to enter the system to eliminate negative pressure.

(2) Description of the Related Art

In the past, one (1) of the problems associated with multi-storydrainage systems was the creation of positive pressure or back pressurein the branch piping. The positive pressure occurred when gases weretrapped in the branch piping. Excessive amounts of gas trapped in thebranch piping can blow water out of the traps of the fixtures connectedto the branch piping. In one (1) instance, the positive pressure iscaused by an overload of waste in the stack. Positive pressure can alsobe caused when waste moves down the stack at an excessive speed, thustrapping the gases in the branch piping. In multi-story buildings, theflow of waste from upper stories accelerates as it moves down the stackdue to gravity. Thus, the higher the entrance point of waste into thestack, the greater the speed attained by the waste and the greater thelikelihood that positive pressure will be created in the lower branchpipings. Systems other than multi-story systems may also have a problemwith positive pressure. Caused when waste is introduced into the stackat a high rate of flow. One such instance is where the system includes awashing machine having a high velocity pump to drain the water.

In the past, drainage systems for multi-story buildings greater thanfive (5) stories contained a vertical vent pipe connected to a verticalwaste or soil stack with branch piping for the various floors extendingoff the waste or soil stack. In these systems, the vent pipe isconnected between the bottom of the waste or soil stack and the top ofthe waste or soil stack. In some instances, the drainage system includedboth a waste stack and a soil stack connected to the vent pipe and thebranch piping. The vent pipe allowed gases to escape from the waste orsoil stack into the vent stack and through the top of the vent stack tothe outside air. For such a system to operate correctly, the vent pipemust be a minimum of half the size of the waste or soil stack. Thus,additional space is needed for the vent pipe. In addition, it isdifficult to retrofit a drainage system with a vent pipe.

U.S. Pat. No. 4,121,914 to Kigawa et al. describes one device foreliminating the need for a separate vent pipe. Kigawa et al. describes adrainage piping system which uses a twisted pipe having an axishelically deviating from the axis of the main pipe. The twisted pipecauses the waste to flow through the main pipe in the form of ahelically swirling descending stream. The twisted pipe reduces thevertical velocity of the descending stream and also causes the stream toflow down the inner surface of the pipe. The twisted pipe ensures thatthe stream flowing down the vertical main pipe will have an air columnextending therethrough in the center of its cross-section to allow gasesto move past the stream.

The drainage system of the present invention relieves positive pressurein the branch piping of a drainage system without the need for aseparate vent pipe. There remains the need for a drainage system whichis easy to install and which eliminates build up of positive pressure inthe branch piping of the drainage system.

SUMMARY OF THE INVENTION

The drainage system of the present invention eliminates positivepressure in the branch piping of the drainage system which eliminatesthe possibility of water being blown from traps through the fixturesattached to the branch piping. One (1) embodiment of the drainage systemalso relieves negative pressure in the branch piping. Negative pressurein a drainage system can drain the liquid out of the traps for thefixtures connected to the branch piping rendering the traps ineffectivein stopping the escape of sewer gases through the fixtures. The positivepressure in the drainage system of the present invention can be causedby waste moving at a high rate of speed down the stack. Such a high rateof speed is achieved in the system where the stack of the system has aheight of at least 480 feet (12191 mm) between the entrance of the wasteand the main drain of the system. The high rate of speed is alsoacheived where the waste is introduced into the system at a high rate ofspeed such as by a high velocity drainage pump. The connection of thestack at a 90° angle to the main drain also helps to trap gases in thestack.

The drainage system of the present invention includes a stack, a branchpiping and a relief vent. The drainage system can also include an airadmittance value to eliminate negative pressure in the drainage system.A fixture with a trap is connected to the branch piping. The relief ventis connected to the branch piping between the stack and the trap of thefixture such that the inner passageway of the relief vent is in fluidcommunication with the inner passageway of the branch piping. If thebranch piping has more than one fixture, then the relief vent isconnected to the branch piping between the stack and the first trap,closest to the stack. The relief vent is a unidirectional vent whichopens automatically upon the application of positive pressure at thefirst end of the passageway of the flexible vent member. The relief ventcloses automatically when the pressure is reduced. In one (1)embodiment, the relief vent closes automatically when the pressure atthe first end of the passageway is less than or equal to atmosphericpressure. In one (1) embodiment, the relief vent includes anelastomeric, flexible vent member which uncurls and separates to formthe passageway to allow the trapped gas to escape the branch piping. Theflexible vent member is positioned within a cover having a body and acap. The sidewall of the cover has openings to allow the gas escapingthe branching piping thru the flexible vent member to exit the coverinto the surrounding air. The relief vent is mounted at a high point onthe branch piping to allow the drains of fixtures to back up into thefixtures during a blockage rather than attempting to exit the drainagesystem thru the relief vent. The relief vent is connected to the branchpiping by a connector. In the drainage system also having the airadmittance valve, the relief vent and the air admittance valve can beconnected to the branch piping at the same point using a Y-connector.The air admittance valve is in fluid communication with the branchpiping and is connected to the branch piping before the trap of thefirst fixture. The air admittance valve is structionally similar andoperates similarly to air admittance valve well know in the art. The airadmittance valve opens upon the application of negative pressure at thefirst end of the inner passageway connected to the branch piping. Theair admittance valve opens to allow air to enter the air admittancevalve and the drainage system. The air admittance valve closesautomatically once the pressure in the branch piping adjacent the firstend of the air admittance valve is greater than or equal to theatmospheric pressure.

The present invention relates to a drainage system, which comprises astack having an inlet and an outlet; a branch pipe connected to thestack at a point spaced between the inlet and the outlet of the stackhaving a drain opening with a vent opening spaced between the stack andthe drain opening; and a relief vent connected to the branch pipe at thevent opening in fluid communication with the branch pipe wherein whengas enters the inlet of the stack and create positive pressure in thebranch pipe, the relief vent opens to allow gas in the branch pipe toescape so as to equalize pressure in the drainage system.

Further, the present invention relates to a drainage system, whichcomprises a stack having an inlet and an outlet; a branch pipe in fluidcommunication with the stack and connected to the stack between theinlet and the outlet of the stack, the branch pipe having a drainopening; a relief vent in fluid communication with the branch pipe andconnected to the branch pipe between the drain opening and the stack andconfigured to open in response to positive pressure in the branch pipeto equalize pressure in the branch pipe; and an air admittance valve influid communication with the branch pipe and connected to the branchpipe between the drain opening and the stack and configured to open inresponse to negative pressure in the branch pipe to equalize pressure inthe branch pipe.

Still further, the present invention relates to a method for equalizingpressure in a drainage system, the drainage system having a stack havingan inlet and an outlet with a branch pipe in fluid communication withthe stack connected to the stack between the inlet and the outlet, thebranch pipe having a drain opening, the method which comprises the stepsof: providing a relief vent connected to the branch pipe at a pointspaced between the stack and the drain opening; providing fluid into theinlet of the stack so that the fluid moves past the branch pipe andmoves into the branch pipe; opening the relief vent in response topositive pressure in the branch pipe adjacent the relief vent; andevacuating gas in the branch pipe through the relief vent until pressurein the pipe valve is equalized.

The substance and advantages of the present invention will becomeincreasingly apparent by reference to the following drawings and thedescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the drainage system 10 showing the reliefvent 16, the air admittance valve 30, the branch piping 14 and the stack12.

FIG. 2 is a cross-sectional view of the relief vent 16 with the flexiblevent member 20 in the closed position.

FIG. 3 is a cross-sectional view of the relief vent 16 with the flexiblevent member 20 in the open position.

FIG. 4 is a prior art drainage system having positive pressure.

FIG. 5 is a prior art drainage system having negative pressure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The drainage system 10 of the present invention includes a stack 12,branch piping 14, a relief vent 16 and optionally an air admittancevalve 30. The stack 12 has opposed ends and is connected at the secondor bottom end to the main drain 100 (FIG. 1). In one (1) embodiment, thestack 12 is connected to the main drain 100 at a 90° angle. The stack 12can be a waste stack 12 or a soil or sewer stack (not shown). In one (1)embodiment, the system 10 includes both a waste stack 12 and a soilstack. The branch pipings 14 (one shown) are connected to the stack 12between the ends of the stack 12. In one (1) embodiment, where thedrainage system 10 is incorporated into a multi-story structure, eachfloor of the structure is provided with a branch piping 14. Each branchpiping 14 has at least one fixture 102 connected thereto. The fixtures102 can be bathroom or kitchen fixtures such as sinks, bathtubs,toilets, etc. A trap 104 is provided between the branch piping 14 andeach one of the fixtures 102 to prevent sewer gases from escaping fromthe drainage system 10 then the fixture 102.

The relief vent 16 is connected to the branch piping 14 between thestack 12 and the trap 104 of the fixture 102. In one (1) embodiment, therelief vent 16 is similar in structure to the valve described inapplicant's U.S. application Ser. No. 10/245,126, which is incorporatedherein by reference in its entirety. However, it is understood that therelief vent 16 can be any type of one-directional valve well known inthe art which opens upon the application of pressure at one (1) end andwhich automatically closes upon a decrease in pressure. The relief vent16, of one (1) embodiment, includes a collar 18, a flexible vent member20 and a cover 22. The collar 18 has a first end 18A and a second end18B with an inner passageway 18C extending between the ends 18A and 18B.The axis of the inner passageway 18C of the collar 18 forms thelongitudinal axis A-A of the relief vent 16. In one (1) embodiment, thecollar 18 has a cylindrical shape. The collar 18 has a first portionadjacent the first end 18A and a second portion adjacent the second-end18B. The inner and outer diameters of the first portion are greater thanthe inner and outer diameters of the second portion, respectively, suchthat a shoulder is formed in the inner passageway 18C and on the outersurface of the collar 18 between the first and second portions. The sizeof the inner passageway 18C of the collar 18 adjacent the first end 18Ais such that the first end 18A of the collar 18 can be mounted over theend of a standard connector pipe 106 which is connected to the branchpiping 14 (FIGS. 2 and 3). It is understood that the collar 18 couldalso be mounted inside of the standard connector pipe 106. The collar 18can be mounted to the standard connector pipe 106 by any well knownmeans.

The flexible vent member 20 is mounted on the second end 20B of thecollar 18 and extends in -a direction away from the first end of thecollar 18 and away from the connector pipe 106. The flexible vent member20 has a first end 20A and a second end 20B with an inner passageway 20Cextending therebetween. The first end 20A of the flexible vent member 20is mounted on the second portion of the collar 18 such that the secondportion of the collar 18 is in the inner passageway 20C of the flexiblevent member 20 and the inner passageway 20C of the flexible vent member20 at the first end 20A is co-axial with the longitudinal axis A-A ofthe relief vent 16. The size of the flexible vent member 20 enables thefirst end 20A of the flexible vent member 20 to be stretched to mountover the second portion of the collar 18. The mounting of the flexiblevent member 20 on the outer surface of the collar 18 ensures that theinner passageway 20C of the flexible vent member 20 is always openadjacent the first end 20A of the flexible vent member 20. The flexiblevent member 20 can be constructed of a durable, flexible resilientmaterial having memory. In one (1) embodiment, the flexible vent member20 is constructed of a specifically formulated elastomeric flexible PVCmaterial such as SUNPRENE™ which will remain flat and which has memory.The first end 20A of the flexible vent member 20 can be mounted to thecollar 18 by any well known means such as by friction fit or by use ofan adhesive. In the normal position, the inner passageway 20C of theflexible vent member 20 adjacent the second end 20B is closed so thatgases can not pass through the relief vent 16. In one (1) embodiment,the second end 20B of the flexible vent member 20 is curled away fromthe axis A-A of the relief vent 16 which acts to close the innerpassageway 20C of the flexible vent member 20. In one (1) embodiment,the second end 20B of the flexible vent member 20 has a J-shape. In thisembodiment, the flexible vent member 20 of the relied valve opens uponthe application of pressure to the inner passageway 20C at the first end20A of the flexible vent member 20. Upon removal of the pressure, theinner passageway 20C of the flexible vent member 20 at the second end20B closes preventing the passage of gas through the relief vent 16.

The cover 22 is mounted on the second end 18B of the collar 18 over thefirst end 20A of the flexible vent member 20 so that the second end 20Bof the flexible vent member 20 extends into the interior of the cover 22(FIGS. 2 and 3). The cover 22 has a first end 22A and a second end 22Bwith a sidewall 22C extending therebetween. The length of the cover 22between the ends 22A and 22B is such that when the flexible vent member20 is in the fully open position, the second end 20B of the flexiblevent member 20 does not contact the second end 22B of the cover 22. Theinner diameter of the cover 22 adjacent the first end 22A is greaterthan the outer diameter of the second portion of the collar 18 with theflexible vent member 20 so that the cover 22 can be mounted over thesecond end 22B of the collar 22. The cover 22 extends outward from thesecond end 22B of the collar 18 away from the first end 18A of thecollar 18. The cover 22 can be mounted over the collar 18 and flexiblevent member 20 by any well known means. The sidewall 22C of the cover 22is provided with openings 24 which allow gas exiting the flexible ventmember 20 to be vented to the outside. In one (1) embodiment, the cover22 is constructed of a body 26 and a cap 28. In this embodiment, the cap28 is mounted on the open second end of the body 26. The cap 28 isremovable to allow access to the flexible vent member 20.

In one (1) embodiment, the relief vent 16 has a compact construction sothat the relief vent 16 can be easily positioned inside the cabinet of afixture 102 or can be easily positioned adjacent a fixture 102 withoutbeing intrusive. The relief vent 16 is constructed of a durable materialwhich is resistant to gases and liquids found in a drainage system 10.The relief vent 16 is constructed so as to be easily incorporated intoany new or existing drainage system 10. The relief vent 16 allows gasesto exit the branch piping 14 before the pressure of the trapped gasesblow the water out of the traps 104 of the fixtures 102 connected to thebranch piping 14. In one (1) embodiment, the relief vent 16 isconstructed so that liquid cannot exit through the relief vent 16.

The relief vent 16 is connected to the branch piping 14 between thestack 12 and the trap 104 for the fixture 102 connected to the branchpiping 14. If the branch piping 14 has more than one (1) fixture 102having a trap 104, then the relief vent 16 is spaced between the stack12 and the first trap 104. Thus, the relief vent 16 is connecteddownstream of all the fixtures 102 of the branch piping 14. In one (1)embodiment, the relief vent 16 is positioned at the highest pointpossible on the branch piping 14. In one (1) embodiment, the relief vent16 is spaced so that in the fully extended open position, the second end20B of the flexible vent member 20 is above the drain openings or normalwater lines for all the fixtures 102 connected to the branch piping 14(FIG. 1). The positioning of the relief valve 16 above the drainopenings or normal water lines allows for the user to determine when thedrain of a fixture 102 is plugged due to a back up of liquid into thefixture 102 or above the normal water line of the fixture 102.

In a first embodiment, the drainage system 10 is a multi-story drainagesystem 10 for a structure having at least five (5) stories. In one (1)embodiment, the drainage system 10 is a multi-story drainage system 10having a stack 12 with a height of at least 40 feet (12192 mm). In one(1) embodiment, each branch piping 14 is provided with a relief vent 16.In another embodiment, only branch piping 14 at the fifth story andabove are provided with a relief vent 16. In another embodiment, thedrainage system 10 is in a structure having less than five (5) stories.In this embodiment, one of the fixtures 102 connected to one (1) of thebranch pipings 14 of the drainage system 10 has a high velocity drainagepump. In this embodiment, all of the branch pipings 14 downstream fromthe fixture 102 or at a lower story from the fixture 102 are providedwith a relief vent 16. In one (1) embodiment, the fixture 102 having thehigh velocity drainage pump is a washing machine.

In one (1) embodiment, the drainage system 10 also includes an airadmittance valve 30 which enables air to enter the branch piping 14 toreduce the negative pressure in the drainage system 10. In one (1)embodiment, the air admittance valve 30 is similar to the air ventdescribed in Applicant's U.S. Pat. No. 6,161,564, which is incorporatedherein by reference in its entirety. It is understood that the airadmittance valve 30 of the present invention can be similar to any airadmittance valve 30 well known in the art. In one (1) embodiment, theair admittance valve 30 is connected downstream from all the fixtures102 of the drainage system 10. In one (1) embodiment, having both therelief vent 16 and the air admittance valve 30, the relief vent 16 andthe air admittance valve 30 are connected to the same connector pipe 106on the branch piping 14 using a Y-connector (FIG. 1).

In use, as waste flows down the stack 12, gases can become trapped inthe stack 12. These gases escape from the stack 12 into the branchpiping 14 which creates positive pressure in the branch pipings 14. Uponthe creation of positive pressure in a branch piping 14, the relief vent16 connected to the branch piping 14 opens automatically to let thetrapped gas escape. Once the pressure reduced to below atmosphericpressure relief vent 16 closes automatically. By closing automaticallyupon the equalization of pressure within the branch piping 14, therelief vent 16 prevents sewer gases from exiting the drainage system 10through the relief vent 16. In one (1) embodiment, the relief vent 16closes before liquid in the branch piping 14 can enter the relief vent16. Thus, water or waste does not exit the drainage system 10 throughthe relief vent 16. The relief vent 16 is positioned before the firsttrap 104 of the branch piping 14 to prevent the positive pressure fromblowing out any of the traps 104 of the branch piping 14. In theembodiment which also includes an air admittance valve 30, the pressurein the branch piping 14 will always be equalized either by the openingof the relief vent 16 to reduce positive pressure to allow gases out ofthe drainage system 10 or by opening the air admittance valve 30 toreduce negative pressure and to allow air into the drainage system 10.

It is intended that the foregoing description be only illustrative ofthe present invention and that the present invention be limited only bythe hereinafter appended claims.

1. A drainage system, which comprises: (a) a stack having an inlet andan outlet; (b) a branch pipe connected to the stack at a point spacedbetween the inlet and the outlet of the stack having a drain openingwith a vent opening spaced between the stack and the drain opening; and(c) a relief vent connected to the branch pipe at the vent opening influid communication with the branch pipe wherein when gas enters theinlet of the stack and create positive pressure in the branch pipe, therelief vent opens to allow gas in the branch pipe to escape so as toequalize pressure in the drainage system.
 2. The drainage system ofclaim 1 wherein the relief vent has an inlet and an outlet with aflexible valve member spaced therebetween, wherein when positivepressure exists in the branch pipe adjacent the inlet of the reliefvent, the valve member moves to an open position to form a passagewaybetween the inlet and the outlet.
 3. The drainage system of claim 2wherein the valve member has a first end and a second end, wherein therelief vent is positioned so that the first end of the valve member isadjacent the vent opening of the branch pipe and wherein in a normalposition, the second end of the valve member is closed.
 4. The drainagesystem of claim 2 wherein the valve member has a first end and a secondend with a flexible sidewall extending therebetween forming an innerpassageway, wherein the first end of the valve member is adjacent thevent opening of the branch pipe, wherein in a normal position, the innerpassageway of the valve member tapers in cross-section from the firstend toward the second end and the flexible sidewall adjacent the secondend of the valve member is curled, wherein when gas is introduced intothe inner passageway of the valve member at the first end, the flexiblesidewall uncurls and the inner passageway of the valve member expandsadjacent the second end such as to allow the gas to exit the valvemember through the second end of the valve member and wherein the gasexiting the valve member reduces pressure in the branch pipe andprevents the fluid from exiting the branch pipe through the drainopening.
 5. The drainage system of claim 1 wherein a second branch pipeis connected to the stack at a point spaced between the inlet of thestack and the branch pipe and wherein the second branch pipe has a drainopening.
 6. The drainage system of claim 5 wherein the second branchpipe has a second vent opening spaced between the stack and the drainopening and wherein a second relief vent is connected to the secondbranch pipe at the second vent opening.
 7. The drainage system of claim1 wherein the branch pipe has a second vent opening, wherein an airadmittance valve is connected to the branch pipe at the second ventopening and wherein the air admittance valve opens in response tonegative pressure in the branch pipe adjacent the air admittance valveso that fluid is able to enter the branch pipe through the airadmittance valve to equalize pressure in the branch pipe.
 8. Thedrainage system of claim 1 wherein an air admittance valve is connectedto the branch pipe at the vent opening and wherein the air admittancevalve opens in response to negative pressure in the branch pipe to allowfluid to enter the branch pipe through the air admittance valve toequalize the pressure in the branch pipe.
 9. The drainage system ofclaim 1 wherein the stack has a height of at least 480 inches (12191mm).
 10. A drainage system, which comprises: (a) a stack having an inletand an outlet; (b) a branch pipe in fluid communication with the stackand connected to the stack between the inlet and the outlet of thestack, the branch pipe having a drain opening; (c) a relief vent influid communication with the branch pipe and connected to the branchpipe between the drain opening and the stack and configured to open inresponse to positive pressure in the branch pipe to equalize pressure inthe branch pipe; and (d) an air admittance valve in fluid communicationwith the branch pipe and connected to the branch pipe between the drainopening and the stack and configured to open in response to negativepressure in the branch pipe to equalize pressure in the branch pipe. 11.The drainage system of claim 10 wherein the relief vent and the airadmittance valve are connected to the drain pipe at a common point. 12.The drainage system of claim 10 wherein the air admittance valve isconnected to a first opening of the branch pipe, wherein the relief ventis connected to a second opening of the branch pipe and wherein thefirst opening is spaced apart from the second opening.
 13. The drainagesystem of claim 10 wherein the relief vent has an inlet and an outletwith a flexible vent member spaced therebetween, wherein when positivepressure exists in the branch pipe adjacent the inlet of the reliefvent, the flexible member moves to an open position to form a passagewaybetween the inlet and the outlet.
 14. The drainage system of claim 13wherein the flexible member has a first end and a second end, whereinthe relief vent is positioned so that the first end of the flexible ventmember is adjacent the branch pipe and wherein in a normal position, thesecond end of the flexible vent member is closed.
 15. The drainagesystem of claim 13 wherein the flexible member has a first end and asecond end with a flexible sidewall extending therebetween forming aninner passageway, wherein the first end of the flexible vent member isadjacent the branch pipe, wherein in a normal position, the innerpassageway of the flexible vent member tapers in cross-section from thefirst end toward the second end and the flexible sidewall adjacent thesecond end of the flexible vent member is curled, wherein when gas isintroduced into the inner passageway of the flexible member at the firstend, the flexible sidewall uncurls and the inner passageway of theflexible vent member expands adjacent the second end such as to allowthe gas to exit the flexible vent member through the second end of theflexible vent member and wherein the gas exiting the flexible ventmember reduces the pressure in the branch pipe and prevents fluid fromexiting the branch pipe through the drain opening.
 16. The drainagesystem of claim 10 wherein a second branch pipe is connected to thestack at a point spaced between the inlet of the stack and the branchpipe and wherein the second branch pipe has a drain opening.
 17. Thedrainage system of claim 16 wherein a second relief vent is connected tothe second branch pipe between the drain opening and the stack.
 18. Thedrainage system of claim 10 wherein the stack has a height of at least480 inches (12192 mm).
 19. A method for equalizing pressure in adrainage system, the drainage system having a stack having an inlet andan outlet with a branch pipe in fluid communication with the stackconnected to the stack between the inlet and the outlet, the branch pipehaving a drain opening, the method which comprises the steps of: (a)providing a relief vent connected to the branch pipe at a point spacedbetween the stack and the drain opening; (b) providing fluid into theinlet of the stack so that the fluid moves past the branch pipe andmoves into the branch pipe; (c) opening the relief vent in response topositive pressure in the branch pipe adjacent the relief vent; and (d)evacuating gas in the branch pipe through the relief vent until pressurein the pipe valve is equalized.
 20. The method of claim 19 whereinfurther in step (d), after pressure in the branch pipe is equalized, therelief vent closes.
 21. The method of claim 19 wherein the stackadjacent the outlet has a bend, wherein in step (b), the bend preventsgas in the stack from moving out of the outlet of the stack and whereinthe gas trapped in the stack moves to the branch pipe and in step (d),the trapped gas is exhausted through the relief vent.
 22. The method ofclaim 19 wherein the relief vent has an inlet and an outlet with aflexible vent member spaced therebetween and forming a passageway,wherein the flexible member has a flexible sidewall, wherein in a normalposition, the flexible sidewall adjacent the outlet of the relief ventis curled toward the inlet of the relief vent and wherein in step (c),when pressure in the branch pipe reaches a certain level, the sidewalluncurls and the passageway opens to allow the gas in the branch pipe toescape to equalize the pressure in the branch pipe.
 23. The method ofclaim 19 wherein in step (b), the liquid is provided into the stack by ahigh velocity pump, wherein a speed of the liquid moving through thestack traps gas along a length of the stack, wherein the trapped gasmoves into the branch pipe and wherein in step (d), the trapped gasescapes through the relief vent.
 24. The method of claim 19 wherein anair admittance valve is provided in the branch pipe and wherein in step(b), as liquid moves down the stack past the branch pipe, a velocity ofthe liquid determines if positive or negative pressure is produced inthe branch pipe, wherein if positive pressure is created in step (b),the gas trapped in the branch pipe opens the relief vent to allow thetrapped gas to escape and wherein if negative pressure is created instep (b), the negative pressure opens the air admittance valve andenables air to enter the branch pipe to equalize the pressure.